Neurotrophic factors have been shown to appear in the rat brain after lesion. This project intends the molecular cloning of the gene encoding for these lesion-induced trophic factors in the brain. During 1985, we developed the assays to produce these factors and test for their neurotrophic activity. A fraction of mRNA, prepared from lesioned rat brain, responsible for neurotrophic activity was found by in vivo translation into proteins in Xenopus Laevis oocytes. During the last past months, we constructed a cDNA library specific for lesioned rat brain in the Bluescribe MB vector. The selection of the positive clones and the sequencing of the corresponding gene is in progress.